ndp
—
control/diagnose IPv6 neighbor
discovery protocol
ndp |
[-nt ] -i
interface [expressions
...] |
ndp |
[-nt ] -I
[interface | delete ] |
ndp |
[-nt ] -s
nodename etheraddr [temp ]
[proxy ] |
The ndp
utility manipulates the address mapping table
used by the Neighbor Discovery Protocol (NDP).
-a
- Dump the currently existing NDP entries. The following information will be
printed:
- Neighbor
- IPv6 address of the neighbor.
- Linklayer Address
- Linklayer address of the neighbor. It could be
“
(incomplete)
” when the address
is not available.
- Netif
- Network interface associated with the neighbor cache entry.
- Expire
- The time until expiry of the entry. The entry could become
“
permanent
”, in which case it
will never expire.
- S
- State of the neighbor cache entry, as a single letter:
- N
- Nostate
- W
- Waitdelete
- I
- Incomplete
- R
- Reachable
- S
- Stale
- D
- Delay
- P
- Probe
- ?
- Unknown state (should never happen).
- Flags
- Flags on the neighbor cache entry, in a single letter. They are:
Router, proxy neighbor advertisement (“p”). The field
could be followed by a decimal number, which means the number of NS
probes the node has sent during the current state.
-A
wait
- Repeat
-a
(dump NDP entries) every
wait seconds.
-c
- Erase all the NDP entries.
-d
- Delete specified NDP entry.
-f
filename
- Cause the file filename to be read and multiple
entries to be set in the NDP table. Entries in the file should be of the
form
hostname ether_addr
[temp
] [proxy
]
with argument meanings as given above. Leading whitespace and
empty lines are ignored. A ‘#
’
character will mark the rest of the line as a comment.
-H
- Harmonize consistency between the routing table and the default router
list; install the top entry of the list into the kernel routing
table.
-I
- Shows the default interface used as the default route when there is no
default router.
-I
interface
- Specifies the default interface used as the default route when there is no
default router. The interface will be used as the
default.
-I
delete
- The current default interface will be deleted from the kernel.
-i
interface [expressions ...]
- View ND information for the specified interface. If additional arguments
expressions are given,
ndp
sets or clears the flags or variables for the interface as specified in
the expression. Each expression should be separated by white spaces or tab
characters. Possible expressions are as follows. Some of the expressions
can begin with the special character
‘-
’, which means the flag specified
in the expression should be cleared. Note that you need
--
before -foo
in this
case.
nud
- Turn on or off NUD (Neighbor Unreachability Detection) on the
interface. NUD is usually turned on by default.
accept_rtadv
- Specify whether or not to accept Router Advertisement messages
received on the interface. This flag is set by
net.inet6.ip6.accept_rtadv sysctl variable.
auto_linklocal
- Specify whether or not to perform automatic link-local address
configuration on interface. This flag is set by
net.inet6.ip6.auto_linklocal sysctl
variable.
no_prefer_iface
- The address on the outgoing interface is preferred by source addess
selection rule. If this flag is set, stop treating the address on the
interface as special even when the
interface is outgoing interface. The default
value of this flag is off.
disabled
- Disable IPv6 operation on the interface. When disabled, the interface
discards any IPv6 packets received on or being sent to the interface.
In the sending case, an error of ENETDOWN will be returned to the
application. This flag is typically set automatically in the kernel as
a result of a certain failure of Duplicate Address Detection. If the
auto_linklocal per-interface flag is set, automatic link-local address
configuration is performed again when this flag is cleared.
basereachable
=
(number)
- Specify the BaseReachbleTimer on the interface in millisecond.
retrans
=
(number)
- Specify the RetransTimer on the interface in millisecond.
curhlim
=
(number)
- Specify the Cur Hop Limit on the interface.
-n
- Do not try to resolve numeric addresses to hostnames.
-p
- Show prefix list. The following information will be printed:
if
- The network interface associated with this prefix.
flags
- The status of the prefix, expressed by a combination of the following
letters:
A
- This prefix can be used for stateless address
autoconfiguration.
L,
O
- This prefix can be used for on-link determination; that is, it can
be used to determine whether a given destination address is
on-link.
D
- There are no reachable routers advertising this prefix.
vltime
- Valid lifetime; the length of time for which the prefix and a
stateless autoconfigured address generated from this prefix can be
used for the source or destination address of a packet.
pltime
- Preferred lifetime; the length of time for which the prefix and a
stateless autoconfigured address generated from this prefix can be
used by upper-layer protocols unrestrictedly.
expire
- This is the remaining time that the prefix is in the valid state.
ref
- The number of kernel references held for this prefix.
-P
- Flush all the entries in the prefix list.
-r
- Show default router list.
-R
- Flush all the entries in the default router list.
-s
- Register an NDP entry for a node. The entry will be permanent unless the
word
temp
is given in the command. If the word
proxy
is given, this system will act as a proxy
NDP server, responding to requests for hostname even
though the host address is not its own.
-t
- Print timestamp for each entry, to make it possible to merge the output
with tcpdump(1). Most useful when used with
-A
.
The ndp
utility exits 0 on success,
and >0 if an error occurs.
The ndp
utility first appeared in the WIDE
Hydrangea IPv6 protocol stack kit. The -I
auto_linklocal flag first appeared in
FreeBSD 8.0.